Process and apparatus for making bearings



June 2,1936. p 2,042,800

PROCESS ANDAPPARATUS FOR MAKING BEARINGS Filed March 9, 1929 2Sheets-Sheet 1 Fig.1-

I I I INVENTOR.

A TTORNEYS.

Patented June 2, 1936 PATENT OFFICE PROCESS AND APPARATUS FOR MAKINGBEARINGS Robert D. Pike, Piedmont, Calif, assignor to Kali! Corporation,Emeryville, Calif., a corporation of Delaware Application March 9, 1929,Serial No. 345,705

Claims.

My present invention relates broadly to a method for centrifugallycasting alloys such as the so-called plastic bronzes, and moreparticularly to the casting of copper-lead alloys which 5 containrelatively high'percentages of the latter.

The object of my invention is to provide new and novel apparatus and amethod or process of procedure, whereby metal alloys may be suecessfullycast centrifugally; and particularly to provide a method and apparatusfor the casting of bushings and cylindrical linings consisting of analloy of copper and lead, wherein the lead content is relatively high.

The use of bushings in constructing bearings is quite extensive andthese bushings take various forms: for instance, they may be composed ofa single metal or of an alloy and in other cases the alloy is reinforcedby a stronger metal. In carrying out my invention, I propose toconstruct my bushings of a high copper-lead base alloy in the form of athin bushing or lining inside of a reinforcing member of strongermaterial such as bronze, steel, aluminum alloy, etc., to which myimproved copper-lead alloy is securely brazed or welded during theprocess of manufacture. A series of alloys containing from 65% to 85%copper and from 35% to lead is particularly dealt with here. This seriesof alloys has a lower coeflicient of friction than the best so-calledhigh grade tin babbitts and it possesses a conductivity for heat whichis three times greater than the latter. It has about the same hardnessas babbitt, but, unlike babbitt, it comprises relatively infusiblemetals having melting points which range from 890 C. to 950 C. In short,in so far as so-called antifriction properties are concerned, thisseries of copperlead alloys. is superior to the babbitt alloys; but,when made by methods hitherto known, it is comprised of Weak metalswhich are liable to crack and pound out under heavy duty service whenused as a bearing because of dendrites of lead which occur in itsmicrostructure, and this fact has prevented its widespread commercialuse. High leaded copper base alloys have hitherto beencastcentrifugally, but by present known methods it is impossible to'makesatisfactory alloys containing, more than at the most 20% oflead. By theuse of my present invention, I am enabled to centrifugally cast alloysof copper and lead containing over 20% of the latter and having agranular microstructure in which large dendrites of lead are absent, andin which the lead is uniformly distributed in the form of minuteparticles. This feature of my iii IJI

invention alone effects a great improvement in the physical propertiesof the alloy, resulting in the making of a virtually new and superiorantifriction metalfbut of greater importance is the application of myinvention to the brazing 5 or welding of a relatively thin layer of myimproved high lead-copper base alloys onto a stronger base of bronze,steel, aluminum alloy, or other suitable metal. My invention isparticularly adapted to the manufacture of bronze 10 backed steel oraluminum alloy backed bushings used in gas engines for bearings or incylinder walls.

In applying my invention, it is necessary to carefully control theessential elements of time 15 and temperature entering into the process.In making a bronze or steel backed bushing, the back may be firstmachined to accurate dimensions, tinned by dipping in a solder of halflead, half tin, and placed in a suitable mold or holder; 20 or theinside may be copper-plated. In this latter case, it should have a finethread cut in the inside face. These threads, I have found, improve theweld. I may also proceed by merely threading the inside face of thebacking and 25 cleaning it thoroughly. If the back is an aluminum alloy,I prefer to merely thread and clean it thoroughly, as suggested above,and then heat the backing before casting the lining to a temperature notin excess of 200 C.

The mold back assembly is then placed in a suitable furnace, preferablyof the electric resistance type, and heated to from 200 C. to 500 C.During the heating, a steady stream of reducing gas is passed throughthe mold and across 35 the exposed face of the bronze back to preventthe formation of a film of metallic oxides, which would interfere withthe subsequent process of welding the copper-lead to its inside face.When at the proper temperature, the mold containing the back istransferred to a spinning device which holds the axis of the back in asubstantially vertical position. The spinning device is so arranged thatwhile spinning, a stream of neutral or reducing gas passes through theback. In the meantime the copper-lead alloy is held in a furnace whichis preferably of the coreless induc tion type. The alloy is held at atemperature of 1093 C. to 1230 0., depending upon the size of bushingcast, the higher temperatures pertaining to' the smaller bushings. Whilein the furnace, the alloy is covered with a suitable protective slag toprevent oxidation. When the centrifugal spinner is up to speed, ameasured amount of the molten copper-lead alloy is drawn into a ladle,

which should be at substantially the same temperature as the metal, andis quickly poured into the spinning back, the spinner being rotated at avery high rate of speed. For example, a

5 bearing which is to have an inside diameter of 2.625 inches is rotatedat from 2500 to 400 revolutions per minute, and other sizes inproportion.

q The molten metal drops vertically into the spin ning back, through theneutral or reducing at- 10 mosphere contained therein, and hits thecenter of a deflector or distributor, which has the same rotationalspeed as the back. This rapidly rotating distributor breaks the metalinto a fine, high velocity spray, which hits the inside face of the 15back and distributesitself thereover in a thin, uniform layer. Thislayer has the desired fine granular microstructure and is securelybrazed or welded to the back.

"If it is desired to cast a bushing of the copper- 0 lead base alloywithout any backing, the same procedure is followed, except that theback described above becomes in effect a mold. I have found that adesirable form of mold is a steel bushing whose inside face has beencalorized. The high 25 copper-lead base metal does not stick to thecalorized surface and may be pushed out by any suitable means.

Having stated my invention in general terms, I shall now describe, byreference to the drawings,

30 an example of its application in practice.

In the drawings- Fig. l is a vertical, fragmentary view in section,showing the detail assembly of the spinning mold and back,

35 Fig. 2 is' a vertical, sectional view of a furnace suitable for usein preheating the mold-back assembly, v

Fig.3 is a side elevation of the assembled spinning apparatus, and

Fig. 4 is a sectional view taken on line IV-IV of Fig. 3.

In the drawings, l0 designates the top of a suitable support for acentrifugal spinner or casting machine, as herein illustrated, thissupport 45 being as shown in Fig. 3 of the drawings in the form of ametallic table; The rotary element or mold in thepresent instance isshown as cornposed of an outer steel shell H having a bottom closuremember l2 which is threaded into the 50 shell II. This bottomclosure-member i2 is shown as provided with a downwardly projectingtapered shank l3. The shank l3 has a hole or gas duct l4 extendingaxially therethrough which communicates with the interior of the 55mold. At the upper end of the shell u there is also provided a topclosure member l6 which is a'lsothreaded into the shell II. In thepresent instance, there is shown a backing member I! located within theshell I I. This backing member l1 may be of bronze, steel, aluminum, orother suitable metal and is machined to fit loosely within the shell Hand is securely held in place between the bottom member i2 and the topmember l6 when they are screwed toward each other in 5 the shell ll.When the backing I 1 is in place, the top closure member I 6 will bescrewed into the shell I l by means of a suitable spanner wrench whichwill exert a suflicient pressure upon the backing I1 to produce tightjoints betweenthe 0 backing l1 and the top and bottom closure members atthe points l8 and I9 respectively so as to prevent any escape of themolten metal to be cast beyond the inner surface of the shell H. The

75 top closure member [6 isprovided with an opening 20 near the centerthereof and the bottom is preheated, as will hereinafter appear.

closure member I2 is provided with an upwardly projecting shank 2i whichis adapted to carry a distributor 22. This distributor 22 maybe made ofany suitable material such, .for example, as graphite or cast iron. Itis constrained to ro- 5 tate with the shank 2| by means of a pin 23which engages in a slot 24 formed therein. When the mold has beenprepared for casting, as above suggested, it is surrounded by a suitableguard which carries insulation. ,In the drawings this guard is shown ashaving a vertically extending cylindrical metallic wall 25 and ahorizontally extending top cover 25'. These members carry a suitableheatinsulating material 26, the insulating material 25 being providedfor the purpose of preventing a too rapid escape of the heat from themold which The guard 25 is mounted upon a post 21 so that it may beraised and turned out of the way when the mold assembly proper is beingset up and removed from the spinning apparatus, the raising of thisguard being effected by means of a foot pedal 28 (see Fig. 4).

After the mold back assembly has been prepared and is ready for thecasting of the lining of an alloy in accordance with my invention, itwill be preheated and assembled with the spinning apparatus, the shankI3 thereof being inserted into a suitable socket in the upper end of avertical shaft 29. The guard 25 will then 30 be placed over the moldwith asuitable pouring spout 30 which is secured to the guard member 25projecting into the interior of the mold through the opening 20 formedtherein. In order to heat the spout 30, I have shown a gas burner 3| asarranged to project a gas flame into the spout cavity.

In Fig. 2 of the drawings, I have illustrated a furnace 33 suitable forpreheating my improved centrifugal mold carrying assembly. This fur-,nace is adapted to be heated to a temperature of approximately 600 C. bya resistance heater coil 34. In this figure of the drawings, the shankI3 of the mold back assembly is shown as resting in the socket 35 formedin the bottom of the furnace. -The socket 35 is shown as communi eatingwith a pipe 36 through which a reducing gas can be introduced into themold assembly as it is heated, the gas so introduced passingupwardlythrough the mold back assembly and out through the opening 20 inthe cover thereof and escaping via the vent 3'! formed in the top of thefurnace and then to the ventilator hood 38. I have found that hydrogenor gases containing much hydrogen are unsuitable as a reducing gas,because the hydrogen becomes absorbed by the metal surface and isreleased when the copper-lead alloy is cast, making the latter porous. Itherefore prefer to employ a hydrogen-free producer gas made by blowingair through hot coke. v

I shall now describe, in connection with Figs. 3 and 4 of the drawings,the mechanical rotation-producing means contemplated'by me. In thesefigures of the drawings, the shaft 29 is shown as mounted vertically inbearings 39 and 40 which are secured to a suitable. steel supportingframe 4|. The shaft 29 is provided with a pulley 42 about which a belt43 driven by a motor 44 passes. The shaft 29 is provided with a stufiingbox 45 at its lower end below the-bear ing 40. This stuffing box 45cooperates with a stationary upwardly projecting tube or pipe 46, bymeans of which gas may be introduced into the mold while it is rotating,this being possible as the upper end of the pipe or tube 46 communicateswith the opening l4 formed in the tapered shank iii of the moldassembly. The pipe 46 is shown as having a suitable fitting 41 whichconnects by means of a flexible tube 48 with suitable valve controlled'gas conduits 49 and 50. The particular gas used may be of any suitablenature, but in carrying out my method of procedure I prefer to use twodifferent gases, the sources of which, when connected as shown in thedrawings, may be independently controlled by valves BI and 52. The twopreferable gases and their sequence of application are as follows:First, when the mold back assembly has been taken out of the heatingfurnace 33 and placed upon the spinning shaft 29, I pass the abovereferred to hydrogen-free producer gas therethrough for a few seconds.This serves to reduce any oxide which may be formed on the inside faceof the backing member I! during transition from the electric furnace tothe spinner; and secondly, after this circulation of hydrogen-freeproducer gas has been completed and just before casting, the carbonmonoxide bearing gas is swept out of the mold back assembly by passingcommercially pure nitrogen therethrough. The mold will then be ready fora casting of the alloy lining or bushing.

In connection with the-use of the above gases, I have found that it ispossible to cast very good bushings of copper-lead alloy in anatmosphere containing as much as 25% carbon monoxide, but the moltenmetal has a tendency to absorb carbon monoxide and to expel it uponsolidifying. 0n the other hand, the metal will absorb little, if any,nitrogen and, as a result, I find it to be of advantage in makingcastings of the highest grade to spray the metal, as will hereinafterappear, through an atmosphere of commercially pure nitrogen. The pipe46, in addition to serving as a means of introducing the above gasesinto the interior of the mold, also serves a further purpose in that itmay be used to dislodge the tapered portion of the mold carryingassembly from the shaft 29. This additional function of the pipe 46 isaccomplished by supporting the member 41 at the lower end thereof uponone end of a pedaloperated lever so that when pressure is exerted uponthe pedal, the pipe 46 will be forced upwardly and thus raise the moldback assembly so that it can be taken outof the shaft 25. The abovelever and pedal are designated in the drawings respectively by thenumerals 53 and 54, the lever 53 be-. ing pivoted upon a shaft 55supported upon the frame 4|. It will be understood that the shaft 46will not be operated in this manner until after the spinning operationhas terminated.

The method of procedure and operation of apparatus herein discosed is asfollows: It will be assumed that it is desired to cast a copper-leadbase alloy containing, for example, 75% copper and 25% lead, and thatthis alloy has been melted to a temperature of from 1093" C, to 1230 C.in a coreless induction furnace under ,a protecting slag, as suggestedabove. A suitable backing member such as the member I! will then beassembled in the mold in the manner as stated above and placed into afurnace such as the furnace 33, where it will be brought to atemperature of about 400 C., a reducing gas being passed through themold assembly during this operation. The mold is then reinoved from thefurnace and placed in position upon the end of the shaft 2E1. The guard25 will then be lowered over the mold and the whole assembly will thenbe started in rotation while the reducing gas, such as the hydrogen-freeproducer gas, will then be passed through the mold for a few seconds. Atthe end of this time the nitrogen gas will then be turned on and themolten alloy, which it will be assumed has in the meantime been drawninto a hot ladle of known capacity, is immediately poured through thespout 30 and into the interior of the mold assembly. As the metal isdischarged from the spout 30, it will fall upon the surface of thedistributor 22, where it will, as a result of the rotation of thespinner, be broken up into a fine spray which will impinge at a highvelocity on the inner surface of the backing member I! and becomedistributed thereover in a uniform thin and dense layer by reason of thegreat centrifugal force due to the high rotative speed of themold. Afterspinning the mold for about thirty seconds following the pouring of themolten alloy, the assembly may be removed from the spinning apparatusand cooled, and the backing I] with its alloy lining may then be removedfrom the mold.

In my co-pending application Ser. No. 345,706, filed at the same time asthis application, I claim, inter alia, the feature of the quicklyremovable mold.

In conclusion, I wish to state that I have constructed apparatus andproduced bushings in accordance with the above disclosure which I havefound topossess many characteristics superior to bushings now availablein that such bushings are much cheaper to manufacture and moreserviceable than those manufactured in accordance with present knownpractice.

From the above, it will be seen that I have provided new and novelapparatus and a method of procedure for forming bushings and linings ofthe copper-lead alloys and, while I have specified above certairpreferred proportions of copper and lead in the alloy, I desire to haveit understood that the term copper base alloy as used in the claims isintended to embrace all alloys containing 60% or more copper; and thatthe term bushing is intended to embrace any hollow cylinder produced inaccordance with the above, irrespective of how and for what purpose itis-employed.

Having thus described my invention, what I claim and desire to secure byLetters Patent is- 1. The method of casting bushings and the like whichconsists in assembling a metallic backing member in a suitable mold,preheating the mold while passing areducing gas therethrough to reduceany oxide formed on the inside of said backing member, and thereafterpassing nitrogen through said mold to sweep away any existing carbonmonoxide, and thereafter pouring the metal while maintaining a fiow ofsaid nitrogen gas through the mold.

2. An apparatus for centrifugally casting bushings and the like, whichcomprises a vertically arranged rotating mold having means whereby asuitable preformed backing member may be retained therein, a distributorlocated substantially midway the ends thereof adapted to rotate withsaid mold and spray the molten metal outwardly into contact with thebacking member by centrifugal force, and means for introducing asuitable gas into said mold while the metal is bein poured.

3. The method of casing a copper-lead alloy, which comprises heating amold, passing a reducing gas therethrough to reduce any oxide with anatmosphere of nitrogen free 0 oxidizing material and of materialabsorbable by the molten copper lead alloy, and pouring said moltenalloy therein.

5. In the method of lining steel bearing shells,

those steps which consist intreating the surface of the shell with amolten metal'and casting a coating of lining metal on the surface of theshell while maintaining the shell substantially free from contact withthe air.

ROBERT D. PIKE.

